This catalog includes a great selection of very rare Mississippian age (347 MM years ago) and Pennsylvanian age (300 MM years ago). The Paleozoic sharks are the first to evolve and the quantity of fossilized specimens is very small. The Paleozoic specimens are incredibly rare compared to the later period sharks, but are still affordable! Note - I added some incredible Nebraska and Iowa pieces from an old collection assembled during 1950-1980s with exceptional Peripristis & Petalodus teeth. These locations are no longer in existence.